NASA Engineering and Safety Center Document #: Version: Technical Assessment Report RP-05-67 1.0 Title: Page #: Independent Technical Assessment of Cassini/Huygens 1 of 116 Probe Entry, Descent and Landing (EDL) at Titan Cassini/Huygens Probe Entry, Descent, and Landing (EDL) at Titan Independent Technical Assessment Performed and Prepared by The NASA Engineering and Safety Center (NESC) May 26, 2005 NESC Request No. 04-069-I NASA Engineering and Safety Center Document #: Version: Technical Assessment Report RP-05-67 1.0 Title: Page #: Independent Technical Assessment of Cassini/Huygens 2 of 116 Probe Entry, Descent and Landing (EDL) at Titan ACKNOWLEDGEMENTS In addition to the NESC ITA Assessment team, the team would like to recognize the following individuals from the JPL Huygens Mission Risk Reduction EDL (MRR) team. The NESC and the MMR teams worked together to assess the overall Huygens EDL risks. JPL Huygens Mission Risk Reduction EDL Team Gentry Lee, Lead Wayne Lee Rob Manning Christine Szalai NESC Request No. 04-069-I NASA Engineering and Safety Center Document #: Version: Technical Assessment Report RP-05-67 1.0 Title: Page #: Independent Technical Assessment of Cassini/Huygens 3 of 116 Probe Entry, Descent and Landing (EDL) at Titan TABLE OF CONTENTS VOLUME I: ITA REPORT ACKNOWLEDGEMENTS .......................................................................................................................2 1.0 AUTHORIZATION AND NOTIFICATION..............................................................................7 2.0 SIGNATURE PAGE (ASSESSMENT TEAM MEMBERS) .....................................................8 3.0 TEAM MEMBERS, EX OFFICIO MEMBERS, AND CONSULTANTS ...............................9 4.0 EXECUTIVE SUMMARY .........................................................................................................10 5.0 OVERVIEW OF ITA PLAN ......................................................................................................13 5.1 Schedule, Milestones, Information Requirements, Products Produced ............................15 6.0 DESCRIPTION OF THE PROBLEM, PROPOSED SOLUTIONS, AND RISK ASSESSMENT .............................................................................................................................17 6.1 Problem.............................................................................................................................17 6.2 Proposed Solutions ...........................................................................................................17 6.3 Risk Assessments..............................................................................................................17 7.0 DATA ANALYSIS.......................................................................................................................20 8.0 OBSERVATIONS AND RECOMMENDATIONS ..................................................................22 9.0 DEFINITION OF TERMS AND ACRONYMS .......................................................................23 10.0 LESSONS LEARNED.................................................................................................................25 10.1 Mission Design .................................................................................................................25 10.2 Aerothermodynamics........................................................................................................25 10.3 Analysis Process ...............................................................................................................26 VOLUME II: APPENDICES Appendix A ITA/I Request Form (NESC-FM-03-002)..................................................................... 30 Appendix B Huygens Aerodynamic Database................................................................................... 32 B.0 Introduction....................................................................................................................................32 B.1 Aerodynamic Database Modifications...........................................................................................33 B.2 Uncertainties ..................................................................................................................................36 B.3 Summary........................................................................................................................................38 Appendix B Figures B-1 Huygens and Genesis Sample Return Capsule Configurations .....................................................33 B-2 Free Molecular/Modified Newtonian Analyses.............................................................................34 B-3 Nominal CA variation with Mach Number....................................................................................35 B-4 Pitch Damping Coefficients...........................................................................................................36 B-5 Nominal CA vs. Mach Number with ESA Uncertainty.................................................................37 B-6 Pitch Damping Coefficients with Uncertainties.............................................................................38 NESC Request No. 04-069-I NASA Engineering and Safety Center Document #: Version: Technical Assessment Report RP-05-67 1.0 Title: Page #: Independent Technical Assessment of Cassini/Huygens 4 of 116 Probe Entry, Descent and Landing (EDL) at Titan Appendix B Tables B-1 Aerodynamic Uncertainties ...........................................................................................................37 Appendix C Huygens Parachute System Evaluation ........................................................................ 39 C.0 Introduction....................................................................................................................................39 C.1 Parachutes Drag Models ................................................................................................................40 C.2 Parachute Opening Loads and Structural Strength ........................................................................42 C.3 Descent Time Calculations and Results.........................................................................................43 Appendix C Figures C-1 Huygens EDL Sequence ................................................................................................................40 Appendix C Tables C-1 Key Parameters for the Huygens Parachutes .................................................................................41 C-2 Huygens Parachute Drag Model Sets.............................................................................................42 C-3 Pilot and Main Parachute Opening Loads and System Strength Summary ...................................43 C-4 Summary of Final Descent Time Calculations ..............................................................................44 Appendix D Atmospheric Properties.................................................................................................. 46 D.0 Introduction....................................................................................................................................46 Appendix D Figures D-1 Minimum/Average/Maximum Density Envelope..........................................................................46 D-2 Examples of Output from Titan-GRAM’s “High Frequency” Perturbation Model.......................47 D-3 Comparison of Density Profiles from Hourdin et al. (1995) GCM and ISO Profile (Coustenis et al, 2003) with original Yelle Density Profiles .........................................................48 D-4 Comparison of Nominal (0% Argon, 1.9% methane mole fraction) TAMWG T0 Density Profile (Yelle, 2004) with original Yelle et al. (1997) Density Profiles....................................................49 D-5 Comparison of TAMWG T0 Density Profiles 0 through 5 (Yelle, 2004a) with Original Yelle et al. (1997) Density Profiles................................................................................................50 D-6 Comparison of TAMWG T0 (nominal) and TA (maximum methane) Temperature Profiles.......51 D-7 Comparison of TAMWG T0 (nominal) and TA (maximum methane) Density Profiles (Yelle, 2004a) with original Yelle et al. (1997) Density Profiles ..................................................52 D-8 Profiles of Equatorial Mean Eastward Wind and Wind Perturbation Standard Deviations, from the Titan-GRAM Model (Justus et al., 2004)........................................................................53 Appendix D Tables D-1 TAMWG October 6, 2004 Titan T0 Profiles and Mole Fractions of Molecular Nitrogen (N2), Argon (Ar), and Methane (CH4), in Percent ..................................................................................50 Appendix E POST2-Based Flight Simulation....................................................................................62 E.0 Introduction....................................................................................................................................62 E.1 Core Trajectory Simulation in POST2...........................................................................................63 E.1.1 Flight and Systems Studies Heritage of POST2 ............................................................................63 E.1.2 6DOF Entry-3DOF Parachute Descent Trajectory ........................................................................63 E.2 Initial States for Entry Vehicle ......................................................................................................65